Generic service switching devices, for example line circuit breakers or residual current circuit breakers, have a front-panel side and an opposite fastening side as well as narrow and broad sides connecting the front-panel and the fastening sides, and comprise at least one first housing shell and at least one covering part, which are connected by first connecting means, which act on the broad sides of the housing shell and the covering part and hold them together whilst forming a peripheral joining line. Furthermore, the insulating housing of generic service switching devices comprises accommodating areas for connection terminals in the region of the narrow sides.
The covering part can be in a form of a second housing shell, which results in an insulating housing formed from two housing half-shells abutting one another at the peripheral joining line.
The first connecting means are conventionally riveted joints. These hold the housing shell and the covering part together at a plurality of riveting points. In this case, the rivet acts on the broad sides of the housing on both sides and passes through the housing interior. The position for the connecting rivets is therefore not freely selectable, but instead riveted joints can only be positioned where the switching device components and assemblies allow room for this in the interior of the device. The riveted joints, often 4-6 in number, for example, are therefore distributed irregularly over the broad side of the housing. In particular, it is not possible to allow first connecting means to act in a known manner in the region of the accommodating areas for the connection terminals since the terminals prevent connecting rivets from passing through there.
If the connection terminals are now in the form of screw terminals and are tightened to a greater extent than is necessary when a connecting conductor is connected, which may easily arise when using conventional working procedures in electrical installation without the use of a special torque screwdriver, it may arise that the two housing parts, namely the housing shell and the covering part, gape wide apart from one another in the region of the connection terminals, the two housings otherwise continuing to be held together firmly by the riveted joints.
This risk arises in particular when using housing parts made from thermoplastic since this material is softer and more flexible than, for example, a thermosetting plastic material. When the clamping screw is tightened to a great extent, however, the housing parts may gape apart from one another locally in the region of the connection terminals even in the case of a thermosetting plastic housing.
Even the surge in pressure forming in the case of a short-circuit switching operation in the interior of the switching device as a result of the switching arc produced at the contact point can result in the housing parts gaping apart from one another at points at which there is no riveted joint to ensure that the housing parts are held together in a stable fashion, i.e. in particular in the region of accommodating areas for the connection terminals.
The action of the housing parts gaping apart from one another is undesirable since moisture and dirt can enter the housing interior via the gap produced in the process and the functional reliability of the device can be impaired.